Hydrocatalytic desulfurization of gas oil



HYDROCATALYTIC DESULFURIZATION OF GAS OIL Roy Purdy Northcott and Ernest (Iarlton Housarn, Sun- .bury-on-Thames, England, assignors to The British Petroleum Company Limited, London, England, a British joint-stock corporation No Drawing. Application March 27, 1956 Serial No. 574,097

Claims priority, application Great Britain April 6, 1955 1 Claim. (Cl. 208-216) This invention relates to the hydrocatalytic desu1furization of petroleum hydrocarbons, more particularly relatively high boiling petroleum distillates such as gas oils.

It is well-known that organically combined sulfur contained in petroleum hydrocarbons may be removed by contacting the hydrocarbons in the presence of added hydrogen at elevated temperature and pressure with a sulfur-resistant hydrogenation catalyst whereby the org'anically combined sulfur is converted into hydrogen sulfide which may readily be removed from the treated hydrocarbons. Such processes are commonly called hydrofining processes and are usually carried out at temperatures within the range 750 to 800 P. which is considered to be optimum for the hydrogenation reaction.

It is known however, that temperatures within this range promote cracking and adversely affect catalyst activity, and it has therefore been considered necessary to operate at pressures within the range 500 to 1000 p.s.i.ga. in order to ensure a satisfactory catalyst activity and life. For the same reason it has been considered necessary to operate at relatively high gas recycle rates of at least 4000 s.c.f./b.

Large quantities of hydrogen are now available from catalytic reforming processes, and as this hydrogen is not normally available at pressures above 450 p.s.i.ga., it would be an advantage to be able to operate the hydrofining process at pressures below 500 p.s.i.ga. with the additional advantage that a plant built to operate at such pressures would be less expensive, since it would not require the use of such expensive pressure-resisting steels. It would also be economically advantageous to be able to operate with low gas recycle rates as the energy required for circulating and heating the gas would be reduced. It has already been disclosed in United States application Serial No. 501,168, filed April 13, 1955, now US. PatentNo. 2,837,465, granted June 3,, 1958, that reduction of the gas recycle rate from 4000 s.c.f./b. to approximately 1000 s.c.f./b. has no adverse effect on catalyst activity or life when operating at pressures of the order of 1000 p.s.i.ga.

It has now been discovered that relatively low gas recycle rates may equally well be used at pressures not exceeding 500 p.s.i.ga. and that a satisfactory catalyst life can be achieved at such pressures by operating at temperatures in the region of 700 F. The desired degree of desulfurization under these relatively mild conditions may be achieved by lowering the space velocity of the feedstock as compared with operation at higher temperatures and pressures.

7 According to the present invention therefore, a process.

for the hydrocatalytic desulfurization of petroleum hydrocarbons, particularly relatively high boiling petroleum hydrocarbons such as gas oil-s, comprisescontacting the hydrocarbons at a temperature within the range-650 to 750 F. and at a pressure Within the range 200-500 p.s.i.ga. with a sulfur-resistant hydrogenation catalyst in the presence of not more than 2000 s.c.f./b. of hydrogen;

The space velocity of-the liquid feedstock will be selected to give the desired degree of desulfurization, In the case of gas oils containing in the region of,.1.0

weight sulfur, desulfurization can generally-be achieved with a space velocity between 1 and 2 v./v./hr; The preferred catalyst consists of, or comprises, the

oxides of cobalt and molybdenum, either as such or in combined form, preferably incorporated with ametal' oxide'support, preferably alumina, although other sulfur: resistant hydrogenation catalyst known in the art may be used. The preferred catalyst may also contain a small.

amount e.g. 0.1 to 6% wt., of fluorine.

The process according to the invention may be oper'- ated with pure hydrogen or with hydrogen-rich gases from a catalytic reforming process or from any other source.

The process of the invention is illustrated by .the following examples: Example 1 Astraight run Kuwait gas oil of 0.8435 specific gravity,

248 to 359 C. ASTM distillation range and 1.30% wt. sulfur was hydrofined over a catalyst consisting of the mixed oxides ofcobalt and molybdenum on alumina. The catalyst contained 15.6% WT. molybdenum and 2.9% Wt. cobalt, expressed as M00 and C00. I

The operating conditions-employed were as follows:

Pressure"; 220 psig. Temperature t 680 F. Space velocity 1.35 v./v./hr. Gas recycle rate 535 s.c.f./b.

Oil and hydrogen were passed downflow through the I reactor. Pure hydrogen was used as make-up gas and hydrogen sulfide was removed from the recycle gas by adsorption in soda-lime.

In a test of 1000 hours duration the sulfur content of the product remained constant at 0.10% wt. as shown in the table below. The hydrogen consumption averaged 130 s.c.f./b.

Hours on stream. 50 250 350 500 600 750 1,000

Organic sulfur in liquid product, percent Weight.- 0.07 0.09 0.10 0.09 0.10 0.09 0.10 0.10

Example 2 The feedstock and catalyst described in Example 1 were used in an experiment carried out under the follow ing conditions:

Downflow operation was employed. Make-up gas was the exit gas from a catalytic reformer containing approxi- Patented Aug. 18, 1959;

mately 75% molhydrogen; -l-lydrogen sulfide was removed fromthe recycle gas by absorption in soda-lime.

In a test of 173 hours duration the sulfur content of the product remained constant at less than 0.1% wt. as shown in the table below. The hydrogen consumption averaged 125 s.c.f./b.

HOUI'S onstream 50 75 100 125 150 173 Organic sulfur in liquid prodnot, percent weight--. 0.09 0. 09 0.071 0.07 0.06 0.08

Example 3 i 1 A blend of 80%'-byvolurne ofjstraight run gas oil and Pressure I 400 p.'s.i.g. Temperature.--; 680 F. Space velocity 1.35 v./v./hr. Gas recycle rate; 1100 s.c.f./b.

Downfiow operation was employed. Make-up gas was thefexit gas from a catalytic reformer containing approximately 68% mol hydrogen. Hydrogen sulfide was removed from the recycle gas by absorption in soda-lime.

' After the catalyst had been used for 275 hours hydrofining the feedstock described'above under various process conditions, a test of 550 hours duration was carried out under the conditions described above. The sulfur content of the product remained constant at 0.11% wt. asshownin the table below. The hydrogen consumption averaged 130 s.c.f./b.

' L The improved desulfurization obtained by using a fluorine-promoted catalyst in the hydrofining of a gas oil is. shown in the following table.

Fluorine Co-Mo promoted Catalyst oxides on (lo-Mo alumina oxides 0n umina Analysis of catalyst:

C00 percent weight- 3.05 2. 54 M001 do 19. 4 16. 1 F do 3. 46 Dimensions of catalyst pellets, inehes %z %2 Operating conditions:

Space velocity v.lv. lhr 1. 35 1. 35 Temperature F 680 680 Recycle rate s c.i.[b 535 5135 Pressure p.s.i.g 220 220 Sulfur content of feedstock, percent weight 1.59 1. 59 Sulfur content of product, percent weight- 0.185 0.125

We claim: V i A process for the hydrocatalytie desulfurization'ofgas oil which comprises contacting the gas oil at a temperature within the range of 650 F. to 750 F. and at a pressure within the range 200-500 p.s.i. ga.-with a catalyst consisting essentially of the oxides-of'cobalt and molybdenum incorporated with an alumina support, said catalyst containing between 0.1% and 6.0% wt. of fluorine and in the presence of not more than 2000 s.c.f./b. of hydrogen, the space velocity of the liquid feedstock being between 1.0 and 2.0 v./v./hr.

7 References Cited in the file of this patent UNITED STATES PATENTS 2,393,288 Byrns Jan. 22,1946 2,577,823 Stine Dec. 11, 1951 2,691,623 Hartley Oct. 12, 1954' 2,718,490 Porter Sept. 20, 1955; 2,756,183 Knox July 24, 1956, 2,760,907 Attane et a1. Aug. 28, 1956: 2,761,816 Sweetser et al Sept. 4, 1956 2,761,817 Sweetser et al Sept. 4, 1956 2,762,853 Jones et al Sept. 11,.1956 2,767,121 Watkins Oct. 16, 1956 2,769,760 Annable et 211. s Nov. 6, 1956 2,769,763 Annable et a1 Nov. 6, 1956- 2,800,430 Porter et a1 July 23, 1957 2,800,431 Porter et al. July 23, 1957 2,837,465 Porter et a1 June 3, 1958' Burton et a1 June 24, 1958 

1. A PROCESS FOR THE HYDROCATALYTIC DESULFURIZATION OF GAS OIL WHICH COMPRISES CONTACTIONG THE GAS OIL AT A TEMPERATURE WITHING THE RANGE OF 650*F. TO 750*F. AND AT A PRESSURE WITHING THE RANGE 200-500 P.S.I. GA. WITH A CATALYST CONSISTING ESSENTIALLY OF THE OXIDES OF COBALT AND MOLYBDENUM INCORPORATED WITH AN ALUMINA SUPPORT, SAID CATALYST CONTAINING BETWEEN 0.1% AND 6.0% WT. OF FLUORING AND IN THE PRESENCE OF NOT MORE THAN 2000 S.C.F./B. OF HYDROGEN, THE SPACE VELOCITY OF THE LIQUID FEEDSTOCK BEING BETWEEN 1.0 AND 2.0V./V./HR. 